Communication apparatuses, such as a mobile phone and a PDA, have various types of input devices as well as an input device provided with buttons, such as a keyboard and a tenkey, as a device for receiving an instruction from a user. Patent Literature 1, for example, discloses a mobile terminal that detects the inclination of the mobile terminal and a gesture, such as “shaking” and “inclining”, as input based on a signal acquired from an acceleration sensor.